- The role of calcium in maintaining bone health is well established. Adequate calcium intake in older adults has been shown to slow the rate of bone loss and reduce fracture risk.
- Calcium supplementation improves the efficacy of prescription therapies that prevent or treat osteoporosis.
- Calcium has also been associated with beneficial effects on high blood pressure, colorectal cancer, obesity, kidney stones, and premenstrual syndrome (PMS) — although the extent of these effects and mechanisms haven’t been fully explored.
The National Osteoporosis Foundation recommends that women under age 50 get 1,000 mg of calcium per day and women over age 50 consume 1,200 mg of calcium per day. This is more than the average 50- to 65-year-old woman consumes in her diet — usually about 500 mg/day or less.
Sufficient calcium intake can theoretically be obtained in the diet. Dairy products are the most common and cost-effective source. Leafy green vegetables, nuts, dried beans, soy products, and calcium-fortified fruit juices and other foods are other sources.
It is important to know about factors that may limit calcium absorption. These include:
- Low levels of vitamin D due to age-related declines in intake, absorption, and skin production
- Consuming excessive amounts of oxalic acid (found in spinach and other greens)
- Consuming large amounts of phytates (contained in grains such as wheat bran)
- Decreased stomach acid due to age or acid-suppressant medication
- Possibly consuming tannins (found in tea)
Fat, phosphorus, magnesium, and caffeine have negligible effects on calcium absorption at usual intake levels.
Some women may have difficulty achieving the recommended intake of calcium from diet. Women who are lactose intolerant, follow a vegetarian diet that excludes dairy products, have poor eating habits, or just don’t eat much dairy may benefit from the addition of a calcium supplement. The two most common forms are calcium carbonate (such as Tums) and calcium citrate (Citracal).
When trying to meet the daily requirement, remember that it’s the elemental calcium that counts -- and no supplement is 100% elemental calcium. Read the labels carefully. For example, calcium carbonate contains 40% elemental calcium. That means 1,250 mg of calcium carbonate provides 500 mg of elemental calcium (1,250 mg x 40%). An easier way to determine the amount of elemental calcium is to look for the recommended daily allowance (RDA). Add a "0" to the end of the percentage listed to find the elemental calcium per serving. For example, an RDA of 50% would mean each serving contains 500 mg of elemental calcium.
Tips to ensure optimal absorption of calcium for bone health:
- Take divided doses of calcium (about 500 mg or less) throughout the day
- Take calcium carbonate with meals
- Allow a significant interval between calcium and fiber or iron supplements
- Drink plenty of water
- Get adequate vitamin D. For women under age 50, a daily intake of 400-800 IU of vitamin D is recommended. For women over 50, 800-1,000 IU of vitamin D is recommended, either through 15 minutes of sun exposure daily (without a sunscreen), diet, or supplementation. If you are deficient in vitamin D you may require more.
Women should avoid calcium intakes greater than 2,500 mg/day, which can increase the risk for hypercalcemia (too much calcium in the blood), which, in extreme cases, can lead to kidney failure.
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